The graphics are not the problem. Great games can be made with simplistic graphics (e.g. Pong, Snake, Pac-Man); they just need to be fun to play.
The core concept is fairly good but it needs improvements. I think it's great that the squares come from all four corners and not a single fixed spot, so you need to be constantly on the move. The best strategy I found is to circle around and through the gaps in order to bundle all the red squares together. And frankly, it's the 'only' strategy because the squares are too fast, new ones appear too often and don't disappear as quickly, so you need to get the red squares close together, otherwise, the screen gets too crowded.
Having to click to show the time (which doesn't update nor does it reset when you die, by the way) is just a bad decision. It's a distraction at a time when you need to concentrate, and it also blocks a small part of the area around you.
Because of this, I don't know the time of my best attempts (I'd say roughly five seconds) because during those I concentrated and didn't distract myself with the timer.
I think you should just either show the timer at the corner of the screen or your final time when you die (with a 'Retry' button).
There's also a significant problem with lag. If you click to show the time, the game slows down and then speeds once the bubble disappears again.
The same happens even during a regular playthrough, as soon as there are too many red squares onscreen at the same time.
This spike in speed can easily kill you. You rely on the blue square to follow your cursor at a certain speed. When that speed decreases, you move the cursor further away to balance it, but then the speed increases again, your square shoots towards your cursor to catch up – and you most likely die.
Delete the squares more often, or just merge them once they overlap.
Here are a few ideas for taking the concept further; use any them or none as you like. They're all geared towards giving players more breathing room, in order to allow other strategies than making circular motions in the center.
– Make the red squares slower. This allows the player to move around a bit more. Best time wins.
– Slow down the squares and add collectable dots which appear at a random place on the screen and award points. This should force players out of their comfortable position in the center and make them take risks. Most points win.
– Keep the speed but add collectable dots. Collecting a dot purges all the squares onscreen. Best time wins.
I'll repeat that I quite like the concept. It just needs some more polishing.
Edit – Bumped up the rating a bit after the game improved.